Yes Scotland, which is campaigning ahead of the 2014 referendum on Scottish independence, said the the level of support was a ‘tremendous achievement this early in the campaign’.

‘The figures show a real sense of momentum all around the country and we have lots of people who have never been involved in politics coming to us and putting their names down,’ said Yes Scotland chief executive Blair Jenkins.

‘There is still a long way to go until we cross the finishing line in the autumn of 2014, but reaching this number of declared supporters this early gives us great confidence for a positive result in the referendum.’

Supporters of the cross-party group are asked to sign a declaration which says that it is ‘fundamentally better for us all, if decisions about Scotland’s future are taken by the people who care most about Scotland, that is, by the people of Scotland’.

But a spokesman for the rival campaign group Better Together, which is opposing independence, questioned the numbers.

‘Their claims of momentum are a nonsense. At this rate, they will have managed to reach their target of convincing a quarter of the electorate exactly a year after the referendum,’ he said.

‘If they want to sign up enough Scots to win a majority, they will still be chasing signatures in 2018.

‘The reality is that the overwhelming majority of Scots are not buying what the separatists are selling.’